Depends on how many squadrons are to be formed. For a seven squadron force, it was thought that three bases were required: Two sqns (+ OCU and OEU) at CGY, three at St Leuchars and the other two at Leeming.
With Leeming being chopped from the list of definite Typhoon bases in one of Hoon's efforts to pretend defence spending wasn't being cut, it's been suggested that the Typhoon force may go down to five or six squadrons.
Another rumour that's going around suggests that perhaps Leeming might get a Typhoon unit or two after all, or, alternatively, you can have hours of er... fun (?) reading the JCA basing study and coming up with permutations that have Typhoons at Marham or Cottesmore...